Nextcloud ServerApplication · Nextcloud
CVE-2018-3761
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedNextcloud Server before 12.0.8 and 13.0.3 suffer from improper authentication on the OAuth2 token endpoint. Missing checks potentially allowed handing out new tokens in case the OAuth2 client was partly compromised.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceNextcloud Server versions before 12.0.8 and 13.0.3 have improper authentication on the OAuth2 token endpoint, where missing validation checks could allow attackers to obtain new tokens if an OAuth2 client was partly compromised.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Nextcloud ServerApplication
< 12.0.8>= 13.0.0, < 13.0.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Nextcloud Server versionCheck the version.php file in the Nextcloud root directory, or navigate to the admin settings page to view the server version under 'Administration' > 'Basic settings'.Affected if The installed version is below 12.0.8, or is 13.0.0, 13.0.1, or 13.0.2.
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Verify OAuth2 app is enabledNavigate to the Nextcloud admin panel, go to 'Apps', and check if the OAuth2 app is listed as enabled. Alternatively, check the apps-enabled folder for oauth2 configuration.Affected if OAuth2 is enabled and the server version falls within the affected range.
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Check OAuth2 client configurationReview the oauth2_clients table in the Nextcloud database, or check the config.php file for any configured OAuth2 clients. Look for client_id and client_secret entries.Affected if OAuth2 clients are configured on an affected server version.
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Inspect OAuth2 token endpoint behaviorExamine the server logs for any OAuth2 token request patterns. Check if the /oauth2/token endpoint accepts requests without proper client_secret validation.Affected if Token requests succeed without full client credential validation on an affected version.
A user is affected if their Nextcloud Server is version 12.0.7 or below, or version 13.0.0 through 13.0.2, and they have the OAuth2 app enabled with configured OAuth2 clients.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data12.0.813.0.3
Upgrade Nextcloud Server to version 12.0.8, 13.0.3, or later to apply the authentication fix.
Fix this in Nextcloud Server
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-3761 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-3761 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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